Dry cleaning solvent



Patented Aug. 5, 1941 signor to The Procter & Gamble Company, Cincinnati, Ohio, a. corporation of Ohio No Drawing. Application August 11, 1938, Serial No. 224,359

6 Claims.

This invention relates to cleaning materials with the use of organic liquids.

Its object is to improve thecleansing power of such liquids by the addition of small quantities of a material of the type described below.

It is already well known to cleanse fabrics,

clothing, metals and other materials by treating them with adry cleaning solvent such as naptha, benzol, carbon tetrachloride, trichlorethylene, Stoddards solvent, or other dry cleaning solvent of the type exemplified by a volatile hydrocarbon or chlorinated hydrocarbon. Such dry cleaning solvents are usually volatile at moderately elevated temperatures, Stoddards solvent being a special naphtha fraction having a boiling point range of 350 F. to 410 F. It is also well known that the cleansing powers of such solvents can be materially enhanced by adding to the liquid a small quantity of certain materials such as benzine soap, or soap containing free fatty acids commonly known as dry cleaners soap, and other materials, some of which are completely soluble,

others only partially soluble in the organic liquids in the proportions used.

My improvement consists in adding to the dry cleaning solvents used for cleansing, such as those above mentioned, a compound of totally different nature which has not hitherto been known to have the property of enhancing the efficiency of such materials as cleaning agents. The compounds which I use are esters possessing a balanced structure, as more clearly hereinafter defined, belonging to the class consisting of a water-soluble aliphatic hydroxy carboxylic acid in which the H of at least one hydroxyl is substituted with an acyl group having from eight to twenty-two atoms of carbon. It is thus seen that these compounds may likewise be said to consist essentially of esters in which an aliphatic organic carboxylic acid is combined with a hydroxyl group of an aliphatic hydroxy carboxylic acid.

I may use as the water-soluble aliphatic hydroxy carboxylic acid in making the compound, any acid or mixture of this class among which the following specific examples may be mentioned: tartaric, gluconic, malic, xylonic, mannonic', arabonic, rhamnonic, citric and trihydroxy glutaric acids. When more than one hydroxyl group is present in these acids, an internal ester or lactone may in some cases be present without impairing the usefulness of the acid in forming the compounds used in my invention.

The organic aliphatic carboxylic acids which may be used for esterifying the hydroxyl group of the hydroxy carboxylic acids in making the compounds may be any fatty acid or mixture of same whether saturated or unsaturated, containing from eight to about twenty-two atoms of carbon per molecule, such as lauric, myristic, palmitic, stearic, arachidic, oleic, linolic, commercial stearic acid, or the mixed acids from tallow, coconut oil, or other natural fats, which terminology I employ in the specification and claims to include both fats and oils. Compounds prepared with the use of saturated fatty acids have been found to be somewhat more efficient than those prepared with the use of unsaturated acids and therefore the former are preferred for use in my invention,

The combination between the above compounds is readily effected by first forming in known way the acid halides such as the chlorides of any aliphatic monobasic carboxylic acids containing from about eight to about twenty-two carbon atoms and causing these acid halides to react with one or more of the aliphatic hydroxy-carboxylic acids, for example in solution in dioxane whereby the corresponding esters are formed. Thus, when a dioxane solution of a mixture of equal weights of tartaric acid and of'the chlorides of commercial stearic acid (usually-consisting of about 53 percent palmitic, 45 percent stearic and 2 percent oleic acids) is boiled under a reflux condenser for from two to six hours, hydrogen chloride gas is evolved and an ester which may be called tartaric stearate is formed. This product may be recovered, for example, by pouring the dioxane solution into water, thus causing the fatty ester to separate as an insoluble phase. The product contains tartaric mono-stearate and di-stearate.

Tartaric stearate, malic stearate, tartaric oleate, the mixture of esters prepared from the mixed fatty acids of coconut oil and malic acid, and gluconic mono-stearate derived from commercial stearic acid and gluconic acid are other examples of compounds formed in this way which act very efliciently in my process.

Thus hydroxy-carboxylic acids which have been either completely or only partially esterified with high molecular weight fatty acids may be employed in the practice of my invention but I have found that the compounds must possess a structure which is balanced as regards the number of esterified hydroxyl groups and the number of unesterified carboxyl and hydroxyl groups. In short I prefer to use only those fatty acid esters which contain at least as many total free hydroxyl and carboxyl groups as there are usual manner.

esterified hydroxyl groups. In other words the ratio of the total number of free hydroxyl and carboxyl groups in the hydroxy acid portion of the ester to the number of esterified hydroxyl groups is at least one. Such compounds possessing this structure are hereinafter referred to as balanced esters of hydroxy-carboxylic acids. I have no explanation to offer for this peculiar phenomenon but the fact remains that of the many compounds I have tested, only those possessing this balanced structure are satisfactory as cleaning assistants, those, whose structures are unbalanced in the above sense, being markedly inferior and inefiicient in the practice of my invention.

For carrying out my invention, I add to the 1 organic dry cleaning liquid, such as Stoddards solvent, an amount of an assistant, for example tartaric stearate, usually ranging between about 0.025 percent and about 0.5 percent of the solvent and agitate the material to be cleaned in this mixture, and subsequently proceed in the Larger amounts of the ester up to four or six percent may be used but I have found that such high concentrations as a rule materials treated with such a solvent are far more readily cleaned, and cleaned to a much higher degree of perfection than when treated with the same solvent without the addition of any of the assistants described herein. This has been repeatedly demonstrated by the results of standardized cleaning tests on materials soiled under standardized conditions with a vaselinelamp-black mixture. The ability of the assistant to remove soil and to keep same in suspension in the solvent is shown not only by the much higher degree of whiteness of fabrics treated with solvents containing the assistants, but also by the marked action in preventing the re-deposition of soil removed from soiled cloths onto clean cloths treated along with the soiled cloths.

The presence of small amounts of water, for

- example one-percent, does not appear to impair to a marked degree the eficiency of the compounds as assistants in the removing of oily soil. Tests have shown that while solvents containing one percent water and percentages of the assistant in the lower range of percentages hereinbefore given, such as 0.05 percent or 0.1 percent are slightly less efficient than the same compositions dry, dry cleaning solvents containing one percent water and higher percentages of assistant, such as 0.2 to 0.4 percent, clean as well as or better than the same compositions in dry condition; The same effect was noted in studying the ability of the assistant to prevent the redeposition of soil on clean fabric treated simultaneously in the same solvent with soiled fabric.

The results of additional tests on fabrics impregnated with the same Vaseline-lampblack soil previously mentioned, and subsequently soaked in a 10% glucose solution (Water soluble soil) and then driedv at 110 C. indicated that the presence of the assistant improved the ability of the dry .solvent to remove oily soil when fixed with watersoluble sugar. The results of further tests conducted on similarly soiled fabric indicated that the assistants used in the present invention were even more effective in removing such soil fixed with glucose when the solvent contained a small amount of water such as one to five percent.

Numerous such tests have been made with the use of various dry cleaning solvents containing various esters of the type previously mentioned, and it has been noted that greatly improved cleansing effects result in every case as compared with blank cleansing operations carried out under the same conditions but without adding any of the aforementioned esters as cleaning assistants to the cleaning solvent.

The above statements of results of experimental work conducted in the development of my invention are given merely to aid in the clear and complete understanding of my contribution to the art and are not intended to limit in any way the scope of the invention as defined in the appended claims.

It should be understood that the ester compounds described herein are not in themselves the subject of my invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. As a new composition of matter possessing improved cleansing power, a dry cleaning solvent in which has been incorporated from about .025

per cent to about six per cent of an ester derived from a water-soluble aliphatic hydroxy carboxylic acid and an aliphatic carboxylic'acid having from eight to twenty-two atoms of carbon, said ester being balanced in that the ratio of the total number of free hydroxyl and carboxyl groups in the hydroxy acid portion of the ester to the number of esterified hydroxyl groups is at least one.

2. As a new composition of matter possessing improved cleansing power, a dry cleaning solvent in which has been incorporated from about .025 per cent to about six per cent of an ester derived from a water-soluble aliphatic hydroxy carboxylic acid and a saturated aliphatic carboxylic' acid having from eight to twenty-two carbon atoms. said ester being balanced in that the ratio of the total number of free hydroxyl and carboxyl groups in the hydroxy acid portion of the ester to the number of esterified hydroxyl groups is at least one.

3.. As a new composition of matter possessing improved cleansing power a dry cleaning solvent in which has been incorporated from about .025 per cent to about six per cent of tartaric stearate.

4. A dry cleaning fluid consisting essentially of a dry cleaning solvent containing from about .025 per cent to about 0.5 per cent of an ester derived from tartaric acid and commercial stearic acid.

5. A dry cleaning fluid consisting essentially of a dry cleaning solvent'containing from about .025 per cent to about 0.5 per cent of an ester derived from malic acid and commercial stearic acid.

6. A dry cleaning fluid consisting essentially of a dry cleaning solvent containing from about .025 per cent to about 0.5 per cent of an ester derived from gluconic acid and commercial stearic acid, the said ester being balanced in that the ratio of the total number of free hydroxyl and carboxyl groups in the hydroxy acid portion of the ester 

